Final answer:
Rawly's initial gravitational potential energy at the top of the hill is converted into kinetic energy and remaining gravitational potential energy as he sleds down. Using the conservation of energy and the formula GPE = mgh, the kinetic and remaining potential energies can be calculated at any point during his descent.
Step-by-step explanation:
Rawly's sledding scenario involves converting his gravitational potential energy (GPE) into kinetic energy (KE) as he descends the hill. The gravitational potential energy can be calculated using the formula GPE = mgh, where m is mass, g is the acceleration due to gravity (approximately 9.8 m/s²), and h is the height above the ground. At the start, atop the 29.5 m hill, Rawly's GPE is 79.0 kg × 9.8 m/s² × 29.5 m. When he has descended 21.0 m, he would be 8.5 m above the ground; hence the remaining GPE is 79.0 kg × 9.8 m/s² × 8.5 m.
As Rawly descends the hill, the initial GPE at the top is converted into KE and any remaining GPE. Considering energy conservation, the sum of the KE and the remaining GPE at any point during the descent is equal to the initial GPE. Therefore, the KE when Rawly is 21.0 m down the hill can be found by subtracting the remaining GPE from the initial GPE.